Ore concentration



Patented Mar. 1 1926f UNITED STATES 1,577,328 PATENT orr cr...

CARL PIERCE LEWIS, OF SAN FRANCISCO, CALIFORNIA, ASSIGNOR '1O KINEBALS' SEPARATION NORTH -AMERICAN CORPORATION, OF NEW YORK, N- Y,., A CORPORA- TION or MARYLAND.

ORE CONCENTRATION.

R Drawing. Application filed J'n1y26,

To all wl zom it may concern:

Be it knownthat I, CARL Prnnon LEWIS, a citizen of the United States, residing at San Francisco, State of California, have invented certain new and useful Improve-,-

ments in Ore Concentration, of which the following is a specification.

This invention relates to ore concentration and is herein disclosed as especially ap- 110 plied to the selective froth-flotation separation of more or less complex ores, with the production of a concentrate, or separate concentrates, relatively rich in the desired minerals, and relatively free from the undesir- 7153 able minerals. It will, however, appear that 'the flotation agents herein disclosed may be applied to collective flotation.

Ores which contain certain metals such as zinc, and more especially those which contain lead and zinc, together with iron and erhaps other values, have hitherto been found diflicult ores to concentrate in forms that made satisfactory products for the smelter. Even in many cases where the ores were comparatively rich, it has been found difficult 'to satisfactorily separate such metals as the lead and zinc constituents sufficiently from each other and from the normally-floatable iron, if present, to enable the ores to be profitably worked. This has often been the case with lead-zinc ore even though the lead was present as galena, the zinc was present as blende, and the iron was present as pyrite.

I have discovered that with a flotation agent such as crude solvent naphtha or certain oi s derived from coal tar, concentrates may be obtained in much more merchantable or smelterable form, especially in freedom from iron, than has hitherto been possible. I have. found that iron-bearing ores of copper and the precious metals may also be made to yield concentrates remarkably free from non if concentrated with such agents. I have found that Xylene is a highly effective constituent of the flotation agents mentioned, especially when it carried naphthalene in solution, as it did in the coal tar oil used. Moreover, certain mix- 50 tures of benzene-series hydrocarbons have been found more effective than individual benzene-series hydrocarbons, especially when 1920. Serial No. 399,008. a

carrying, in admixture or solution, naphthalene or certain naphthalene derivatives.

By adjusting the amount of hydrocarbons or mixtures used I have, for example, been able to efl'ect a remarkabl complete recovery of zinc singularly ree from iron, thus greatly-enhancing the value of the concentrate. I have also discovered that when such a hydrocarbon, especially a xylene contaimng naphthalene or certain other heavy hydrocarbons is used as a froth-flotation agent insmall amounts on such ores, say around three-quarters of a poundto apound and a half per ton of ore, a concentrate rich 1n lead and poor in zinc and iron'may be obtained; and the tailings from this treatment, with the addition of another similar or smaller, quantity of such hydrocarbon. even omitting the naphthalene ingredient, can be concentrated to recover an extraordinarily large proportion of the zinc comparatively free from lead and iron. -Working in this way the recovery of lead may oftenvbe substantially improved and obtained at lower cost partly owing to the relative low (price of naphthalene. lhe presence of the naphthalene and a benzene-series hydrocarbon in the tailings from the lead treatment in no way interferes with, and sometimes appears to facilitate, the clean recovery of a relatively large proportion of zinc.

I have found that benzene itself is not as efficient as the higher members of the series under most conditions. A mixture of the heavier hydrocarbons of this series, such as is sold under the name of. solvent naphtha, is usually more efficient than would be supposed from a comparison of the results obtained by using the pure hydrocarbons higher up in the series. In effecting the concentration of lead and zinc in the manner described, there is often also effected a very complete recovery of gold and silver, variously divided among the concentrates, and the same is true of copper.

I have discovered that anthracene may be used instead of naphthalene. Anthracene differs from naphthalene in containing three benzene nuclei instead of the two benzene nuclei in naphthalene.

Naphthalene or the benzene series hydrocarbons may be used in connection with a small amount of other frothing agent, such as pine oil. Naphthalene dissolved in pine oil confers on the solution some selective powers, but owing to the necessary predominance of the pine oil in such a solution, the selective effect of the naphthalene is somewhat masked in the absence of benzeneseries hydrocarbon, or its equivalent. It will be observed that naphthalene may be used in solution as a collective frot ing agent when it is not desired to effect selective collection of minerals.

A solution of naphthalene in Squihbs liquid 'petrolatum (sold as containing upwards of 99% napthenes) has substantially the advantages of a xylene solution of naphthalene.

Phenol and the cresols are less satisfactory since I find that they tend to cause a collective float, i. e., they fail to reject the iron pyrites.

It should be noted in connection with all the above named aromatic series flotation agents that one of their remarkablecharacteristics is their non-interference with selection of zinc over iron if used for the selection of lead prior to the flotation of the In a number of tests a thousand grams of the ore were ground in a laboratory ball mill at normal temperature making a one to one pulp. As a rule eighty mesh grinding was found suflicient. The pulp placed in a laboratory flotation machine of the subaeration type and diluted with tap water to make a pulp of 3.5 parts water to one of ore, was then agitated slowly (say at a peripheral speed of 900 feet per minute) while a saturated solution of naphthalene in xylene was added to the pulp at the rate of 0.8 pounds per ton of ore treated. This mixture was then agitated at full speed, that is, at 1700 peripheral feet per minute for a two-minute period, after which opening the air port introduced air, with the formation of a min eral-bearing froth, which was removed during a ten-minute period, after which time very little froth formed. A spitzkasten machine on a number of ores gave similar results. Heating the pulp often improved the selection and the recovery.

The concentrate thus produced from Gnome Mining Co. lead-zinc ore was 9.0% pf the original weight, and assayed as folows:

Assay. original. Silver 18. 05 oz. 62. 6 Lead 60.4% 91.0 Zinc 7.5 16.0 Copper 2. 94 49. 4 4 Iron 4. 3 8. 8 111801 5. 3

To the remaining pul were then added 2.3 poundsper ton of xy ene. This mixture was given agitation at full speed for a two minute period, after which air. was introduced to the pulp and the operation continued and the froth removed. Theconcentrate, when assayed, was found to be 11.1%

of the original weight and to contain the following:

of Assay. original. Silver -5 6. 32 oz. 27. 4 Lead 4. 8% 9.0 Zinc 29. 8% 80. 2 Copper 2. 0% '41. 6 Iron 9. 0% 23.0

The tailings contained 68.2% of the iron but only 10% of the silver, 9% of the copper, 3.8% of the zinc and no lead.

To obtain. a further concentration the lead concentrate obtained as above described was'placed in the machine while 1.3 pounds per ton (of the weight of original ore) of a saturated solution of naphthalene in xylene were added together \vitht'ap water at normal temperature to fill the machine to the proper level; meanwhile being slowly'agitated. After two minutes agitation at full speed, air was introduced to the pulp and as the operation continued, a mineral bearing froth was removed. This cleaner concentrate constituted 6.4% of the original ore and on assay was found to contain the following:

%of Assay. original. Silver 17.20 oz. 42.5 Lead 69.8 73.5 Zinc 6.6 10.0 Copper 2.08% 24.8 Iron 3.0 4.4 Insol 1.0

The residual pulp constituted the lead middling and was removed. Its assay was as follows:

The zinc concentrate obtained as above de-'- the finished zinc concentrate constituting 6.5% of the weight of the original ore and was found to assay as follows:

The residual pulp constituted the zinc T middling, amounting to 4.6% of the original ore, and assayed asfollows:

I Assay.

Silver. 4. 31 oz. Lead 2.3 Zinc '5 24;}; Copper 0 Iron 11.2

Bluff & Fairview mixed ores of the Britannia Mining Company gave the recoveries summarized below when treated analogously as follows: Treatment A (to roduce rougher copper cencentrates) caronate of soda 8 poundsand saturated solution of naphthalene in xylene 1.2 per ton, froth removed during 8 minutes. Retreatment A (to produce cleaner copper concentrates A, and middlings A) 0.4 lbs. per ton of same xylene solution, froth removed during 5 vminutes. Treatment B (to produce rougher zinc concentrates) 1.8 lbs. xylene per ton, froth removed during 14 minutes. Retreatment B (to roduce cleaner zinc concentrates B and middlings B) 0.7 lbs. xylene per ton, froth removed during 12 minutes.

Assay. recovery.

Wt. Cu. Zn. Fe. Cu Zn. Fe. 11;.

Heads 100. 0 2. 35 4. 6 12. 8 100. 0 100. 0 100. 0 Cone. A. 9. 3 19. 92 14. 8 25. 0 78. 8 29. 4 18. 2 Midds. A" 6. 8 4. 15. 8 34. 8 13. 3 22. 9, 18.6 00110. 3.3 1.44 59.8 2. 0 2. 0 42.4 5 Midds. B" 1. 6 l. 72 15. 0 15. 4 1. 2 5. 3 2. 0 Tailing 79.0 14 No. 9. 8 4. 7 60. 7

' 4.9% lead, and 9% iron, recovering 81.2%

of the zinc. I

A similar two-stage treatment of ore from the Golconda Mine at Kingman, Arizona, of

B the Highland Mining and Milling Company, similar to the Gnome ore, but using sodium sulphide at the rate of 3 lbs. per ton of ore, worked out as follows, neglecting the trace of lead:

- Assays.

Wt.% Au. Ag. Cu. Zn. Fe.

Heads 1000 .05 0.60, .63 12.5 8.8 Gone. '11" ;g3 0.10 35.0 3.20 7.6 31.2 06 16. 13".... .3 0.10 21.6 1.12 44.8 6.8 8118 66.4 .01 1.3 .06 1.8 6.0

Recoveries.

Ag. Cu. Zn. Fe.

' Simon silver-lead ore of Mina, Nevada,

temperature. The results are summarized below:

Assays.

% -Wt. Oz. A'g. Pb. Zn. Fe. %Insol Feed 100.0 4. 50 6.3 7.6 6.5

Pb. Conc 7. 9 35. 72 63. 1 5. 6 2. 7 11. 2 Zn. Cone 15. 1 8. 0 s. s 38. 4 7. 5 13. s Tails 77.0 0.6 Tr 1.6 6.7

r Recoveries.

Ag. Pb. Zn. Fe.

Feed 100. 100.. 100. 100. Pb. Cone 63. 0 7e. 2 5. 7 a. 2 Zn. Conc 26.9 20.8 76.3 17.4 Tails. 10.1 18.0 79.4

The ore of the Tomboy mine of Telluride, Colorado, gave better recoveries but with concentrates slightly less clean when subjected to three-stage treatment, followed by retreatment of the third concentrate; first (A) With five pounds of carbonate of soda and 0.2 pounds of methyl alcohol solution of naphthalene; second (B) with 0.2 pounds of the samenaphthalene solution; third (C) with 0.7 pounds of-heavy naphtha from coal tar, and retreatment of the third concentrate with 0.3 pounds of the same naphtha. The results are summarized below:

Assays.

%Wt. Au. Ag Cu Pb. Zn. Fe

.097 1.87 1.10 4.0 5.4 0.4 .19 14.3 7.00 47.0 0.4 12.0 .39 10. 5 0. 1s. 4 22. 0 15. 4 .50 4. 8 2. 30 7. 0 44.0 11.1 .50 0.5 .44 1.1 3.9 27.7 .005 .00 11 No. No. a.

Recoveries.

Au. Ag. Cu. Pb. Zn. Fe

Heads 100.0 100.0 100.0 100.0 1000 100.0 00110.5. 12.1 49.0 42.7 00.0 7.0 .120 0000.13 17.2 24.7 31.1 17.9 18.3 10.7 00110.0 42.2 21.0 17.1 14.0 70.4 14.7 Mid 25.0 1.0 1.9 1.3 3.7 21.8 T0110 3.5 3.1 7.2 40.9

Not only can the present invention be used to make possible the froth-flotation separation of ores hitherto considered commercially unworkable by flotation, such as the mixed lead, zinc and iron ores, but it improves the froth-flotation separation of other ores. Among other advantages it can easily be so operated as to keep the calcium fiuoridecontent of concentrates well within the limits set by the smelters.

Ore of the Emma mine, at Eholt, British Columbia, made into a 3.5 to 1 pulp with tap water at normal temperature gave the following results:

flotation agent, consisting of nine parts of a solution of naphthalene in crude solvent naphtha and one part of Pensacola #350 was used at the rate of 1.4 lbs. per ton o ore. The Pensacola #350 is a crude pine oil made by destructive distillation of wood.

Nevada Douglas Copper Company ore 'from Ludwig, Nevada, containing 3.16%

copper and 13% iron when concentrated in a subaera-tion type laboratory testing machine using commercial crude solvent naphthe. as a flotation agent, produced a concentrate containing 26.2% copper and 28 to 29% iron; recovering more than 90% of the copper, while the tailings contained 60% of the 11'011.

Ore from the Le Roi mine, Rossland British Columbia, containin .25 ounces 0t gold, 2.38% of copper, 30. 7% iron, and 37 .49% insoluble, when concentrated with 2.9 pounds per ton of Barret N o. 1 oil mixed with .2 pounds per ton of crude pine oil yielded a concentrate containing 1.18 ounces gold, 12.96% copper, 35.4%, giving a recovery of 96.8% of gold, and 96.2% of copper. The tailings contained 78% of the origmal iron. When the pulp temperature was raised from its normal temperature of 50 F. to 90 F. the concentrates were richer and the separation more rapid.

The No. 1 oil was found to contain of naphthalene on distillation.

The froth-flotation concentration of the Knob Hill ore of Republic, Washington, was eiiected in a single step, with a mixture containing solvent naphtha, nine parts, and one part of the crude pine oil, known as Pensacola #350. The mixture was used at the rate of 1.2 lbs. per ton of ore.

The concentratw contained 99.9% of both the gold and the silver, and the tailings contained 78.1% of the iron.

A copper-iron ore from Sunlock Minin Cos. mme, Vancouver Island, B. 0., treated similarly to the Knob Hill ore as above de scribed produced a concentrate assaying copper and containing 98% of the original copper.

Even such a refractory ore as Sullivan I lead-zinc ore of Kimberley, B. C. "gave excellent results when concentrated first with ten pounds of carbonate of soda and 0.8 lbs. of a saturated solution of naphthalene in xylene (both per ton of ore), and then concentrated with 1.6 lbs. xylene combined with 0.6 lbs. benzene, all as outlined above. The results are itemized below. The first portion of froth formed after the addition of the naphthalene solution was collected sepa rately as a lead concentrate. The remainder of the same froth was collected as a lead middling. The froth following the addition of the benzene mixture was similarly collected as a zinc concentrate and a zinc mid- (lling.

Assays. recovery.

Wt.% Pb Zn. Fe Pb. Zn. Fe.

Heads 100.0 12.3 17.9 29.4 100.0 100.0 100.0 Pb.0on0s 11.1 00.0 8.0 9.0 54.4 5.0 3.7 Pb. Midds 0.0 50.2 15.5 9.0 24.3 5.1 1.0 Zn. 001100-".-. 22.4 5.0 50.0 9.0 9.1 00.2 7.5 Zn. Midds 7.8 9.2 34.0 18.8 5.0 14.7 5.0 Teilings 52.7 1.5 4.1 45.0 0.4 12.0 91.0

The hitherto refractory Anaconda zinc ore gave remarkable results. The ore wetground to about 80 mesh, made into a 3.5 to

v1 pulp with tap'water at normal temperaing 1pulp was added 2.1 lbs. of crude solvent nap the per ton of original ore and the zinc concentrate froth removed fora period of twenty-six minutes. No retreatments were made. I

Assays.

9' Oz. 7 7 7 1 wt. 8g. 05. Pii. Zn F3.

Heads 100 240 .65 8.5 13.5 12.8 Pb. Cone 9.0 4.56 2.60 58.5 11.5 4.1 2.0 Zn. Cone 26.7 5.30 1.36 11.8 46.0 5.3 3.0

Tailings 64. 3 0. 92 0. 08 0. 1 0. 3 17. 4

Recoveries.

Ag. Cu. Pb. Zn Fe.

Heads -5 100-0 100.0 100.0 100.0 100.0 Pb. Conc. 17.2 36.2 62.3 7.7 2.8 Zn. Conc 58. 2 56. 1 37. 0 90. 9 10. 9 Tailings 24. 6 7. 7 0.7 1. 4 86. 3

is especlally called to the low iron content of the concentrates, over 86% of the iron being discarded with the tailings.

The amounts of reagents set forth above are examples only and are subject to change to suit the needs of varying working con itions and of different ores. So also the working conditions, if any, will be adjusted to different ores. As is well known in the art the exact working conditionsfor best re sults in the treatment of any ore can only be determined in practice.

I claim:

1. The process of concentrating ores which consists in mixing with an ore pulp a flotation agent including a heavy hydrocarbon carried in a hydrocarbon of the benzene series and dependent upon the presence of a substantial amount of both kinds of hydrocarbon for froth-producing properties, and also bringing gaseous bubbles into contact with the solid particles in the ore pulp so as to produce .a mineral-bearing froth carrying a large proportion of a mineral of the ore, and separating the froth.

2. The process of concentrating ores which consists in mixing with an ore pulp a mineral-frothing agent substantially dependent on the presence of a heavy hydrocarbon and a benzene-series hydrocarbon in the-absence of soapy material to produce a mineral-bearing froth, and also bringing gaseous bubbles into contact with the solid particles in the ore pulp so as to produce mineral-bearing froth, and separating. the froth.

3. The process of concentrating ores which consists in mixing with an ore pulp a miner al-frothing agent substantially dependent onthe presence of an aromatic compound containing a plurality of benzene nuclei carried in a benzene-series hydrocarbon in the absence ofsoapy material to roduce a mineral bearing froth, and also ringing gase ous bubbles into contact with the solid par ticles in the ore pulp so as to produce mineral-bearing froth, and separating the froth.

4. The process of concentrating ores which consists in mixing with an ore pulp a mineral-frothing agent substantially dependent on the presence of an aromatic hydro-carbon containing a plurality of benzene nuclei carried in a benzene-series hydrocarbon in the absence of soapy material to produce a minoral-bearing froth, and also bringing gaseous bubbles into contact with the solid particles in the ore ulp so as to produce mineral-bearing frot 1, and separating the froth.

5. The process of concentrating ores which consists in mixing with an ore pulp a mineral-frothing agent substantiall dependent on the presence of an aromatic ydrocarbon containing a plurality of benzene nuclei carried in a liquid hydrocarbon of the benzeneseries in the absence of soapy material to produce a mineral-bearing froth, and also bringing gaseous bubbles into contact with the solid particles in the ore pulp so as to produce mineral-bearing froth, and separat ing the froth.

6. A process of concentrating ores con taining zinc and normally fioatab-le iron which consists in mixing with a pulp of such an ore a small enough quantity of a mineralfrothing agent substantially dependent on the presence of a benzene-series hydrocarbon to produce a mineral-bearing froth selective of zinc over iron, and also brin ing gaseous bubbles into contact with the so id particles in the ore pulp so as to produce a mineralbearing froth carrying a relatively large proportion of the zinc and a relatively small proportion of the iron'so as to obtain a concentrate relatively rich in zinc.

7. A process of concentrating ores containing zinc and normally floatable iron which consists in mixing with a pulp of such an ore a small enough quantity of a mineral frothing agent substantially dependent on the presence of crude solvent coal-tar naphtha to produce a mineral-bearing froth selec tive of zinc over iron, and also bringing gaseous bubbles into contact with the solid particles in the ore pulp so as to produce a mineral-bearing froth carrying a relatively large proportion of the zinc and a relatively small proportion of the iron so as to obt-am a concentrate relatively rich in zinc.

8. A process of concentrating ores containing zinc and normall fioatable iron which consists in mixing ,wit a pulp of such an ore a small enough quantity of a mineral-froth ing agent substantiallv dependent on the presence of a benzene-series hydrocarbon carrying napthalene in solution to produce a mineral-bearing froth selective of zinc over iron, and also bringin gaseous bubbles into contact with the soli particles in the ore pulp so as to produce a mineral-bearing froth carrying a relatively large proportion of the zinc and a relatively small proportion of the iron so as to obtain a concentrate relatively rich in zinc.

9. A process of concentrating complex ores which consists in mixing with a pulp of such an ore a small enough quantity of a mineral-frothing agent substantially dependent on the presence of napthalene insolution to produce a mineral-bearing froth, and also bringing gaseous bubbles into contact with the solid particles in the ore pulp so as to produce a mineral-bearing froth relatively rich in one constituent of the ore, separating the froth concentrate, mixing with the remaining pulp benzene-series hydrocarbon material, bringing gaseous bubbles into contact with said remaining pulp so as to produce a second mineral-bearing froth relatively rich in a second constituent of the ore, and separating the second froth.

10. A rocess of concentrating complex ores which consists in mixing with a pulp of such an ore a small enough quantity of a mineral-frothing agent substantially dependent on the presence of a benzene-series hydrocarbon having naphthalene in solution to produce a mineral-bearing froth selective of zinc over iron, and also bringing gaseous bubbles into contact with the solid particles .in the 'ore pulp so as to produce a mineralbearing froth relatively rich in one constituent of the ore, separating the froth concentrate, mixing with the remaining pulp a further amount of frothing agent, bringing gaseous bubbles into contact with said remaining pulp so as to produce a second mineral-bearing froth relatively rich in a second constituent of the ore, and separating the second froth.

11. A process of concentrating ores containin threermetals which consists in mixing with the pulp of such an, ore a small enough quantity of a mineral-frothing agent substantially dependent on the presence of a benzene-series hydrocarbon to produce mineral-bearing froth selective of one metal over another, and also bringing gaseous bubbles into contact with the solid particles in the ore pulp so as to produce a mineral-bearing froth relatively rich in the first metal,

bubbles into contact with separating;- the froth, mixing with the remaining pulp a mineral-frothing agent substantially dependenton the presence of henzene-series hydrocarbon material to produce a mineral-bearing froth, also bringing gaseous bubbles into contact with the sol1d par ticles in the ore pulp so as to produce a mineral-bearing froth relatively rich in the second metal, and separating the froth relatively rich in the second metal to obtain a second concentrate containing a relatively small proportion of the first and third metals. 12. A'process of concentrating ores containing lead, zinc and normally fioatable iron which consists in mixing with a pulp of such an ore a mineral-frothing agent substantially dependent on the presence of a benzene-series hydrocarbon to produce a mineral-bearing froth selective of lead over zinc and iron, and also bringin gaseous 'the solif particles in the ore pulp so as to produce mineralbearing froth relatively rich in lead, separating the froth, mixing with the remainder of the pulp a further amount of mineralfrothing agent substantially dependent on the presence of benzene-series hydro-carbon material to produce a mineral-bearing froth, and also'bringing gaseous bubbles into con tact with the solid particles in the ore pulp so as to produce mineral-bearing froth rela' tively rich in zinc, and separating the froth so as to obtain a relatively large proportion of the zinc.

13. A process of concentrating ores containing lead, zinc and normally fioatable iron which consists in mixing with a pulp of such an ore a mineral-frothing agent substantially dependent 'on the presence of crude solvent coal-tar naptha to produce a mineral-bearing froth selective of lead over zinc and iron and also bringing gaseous bubbles into contact with the solid particles in the ore pulp so as to produce mineral-bearing froth relatively rich in lead, separating the froth, mixing with the remainder of the pulp a further amount of mineral-frothing agent to produce a mineral-bearing froth, and also bringing gaseous bubbles into contact with the solid'particles in the ore pulp so asto produce mineral-bearing froth relatively rich in zinc, and separating the froth so as to obtain a relatively large proportion of the zinc.

14. A process of concentratin taining' lead, zinc and normalfy ores confloat-able .iron which consists in mixing with a pulp 'taining mixing with the remainder of the pulp a further amount of mineral-frothing agent substantially dependent on the presence of benzene-series hydrocarbon material to roduce a mineral-bearing froth, and also brmging gaseous bubbles into contact with the solid particles in, the ore pulp soas to roduce mineral-bearing froth zinc, and .separating the froth so as to obtain a relatively large proportion of the zinc. 15. A lprocess of concentrating ores conead, zinc and normally floatable iron which consists in mixing with a pulp of such an ore a mineral-frothing agent substantially dependent on the presence of ben- Zeno-series hydrocarbon material carryin napthalene in solution to produce a minera bearing froth, and also bringin gaseous bubbles into contact with the soli particles in the ore ulp so as to produce mineralbearing frot ing the froth, mixing with the remain er of the pulp a further amount of mineral-frothing agent substantially dependent on the presence of benzene-series hydrocarbon material to produce a mineral-bearing froth,-

and also bringing gaseous bubbles into contact with the solid, particles in the ore pulp so as to produce mineral-bearing froth relatively rich in zinc, and separating the froth so as to obtain a relatively large proportion of the zinc.

16. A process of concentrating ores containing zinc and normally floatable iron which consists in mixing with a pulp of such an ore a small enough quantity of a mineralfrothing agent substantially dependent on the presence of a benzene-series hydrocarbon carrying a solid hydrocarbon to produce a mineral-bearing froth selective of zinc over iron and also bringin gaseous bubbles into contact with thesoli particles in the ore pulp so as to produce a mineral-bearing froth carrying a relatively large proportion of the zinc and a relatively small proportion of the iron so as to obtain a concentrate relatively rich in zinc.

17. A process of concentrating complex relatively ric in relatively rich in lead, se arat-.

ores which consists in mixing with a pulp of such an ore a small enough quantity of a ing pulp so" as to product. second mineralhearing froth relatively rich in a secondconstitutent of the ore, and separating the second froth.

18. A process of concentratin ores which consists in mixing with a pulp of such were a small enough quantity of a mineral-frothing agent substantially deendent on the presence of a solid hydrocarn dissolved in-a volatile solvent to produce a mineral-bearing froth selective of one mineral constituent over another of the ore and also'bringing gaseous bubbles into contact with the solid particles in the ore pul so as to produce a mineral-bearing frot relatively rich in one constituent of th ore, separating the froth concentrate, mixing with the remaining pulp a further quantity of frothing agent, bringing gaseous bubbles into contact with said remain-. ing pulp so as to produce a second mineralbearlng froth relatively rich 1n a second constituent of the ore, and separating the second froth.

19. The process of concentrating ores which consists in subjecting a pulp of the ore to froth-flotation separation with a min-- eral frothing agent substantially dependent on the presence of crude solvent coal-tar naptha in the absence of soapy material to produce a mineral-bearing froth, and sepa rating the froth selective of a mineral of the ore. e

In testimon whereof, I have aflixed my signature to t is s ecification.

' CA L PIERCE LEWIS.

complex v 

